The present invention relates generally to an improved dispensing and sealing system and, more particularly, to an improved dispensing and sealing system that is adapted to produce foam-in-place packaging cushions.
Foam-in-place packaging is a highly useful technique for on-demand protection of packaged products. In its most basic form, foam-in-place packaging comprises injecting foamable compositions from a dispenser into a container that holds a product to be cushioned. Typically, the product is wrapped in plastic to keep it from direct contact with the rising (expanding) foam. As the foam rises, it expands into the remaining space between the product and its container (e.g. a box formed of corrugated paperboard), thus forming a custom cushion for the product.
A common foaming composition is formed by mixing an isocyanate compound with a hydroxyl-containing material, such as a polyol (i.e., a compound that contains multiple hydroxyl groups), typically in the presence of water and a catalyst. The isocyanate and polyol precursors react to form polyurethane. At the same time, the water reacts with the isocyanate compound to produce carbon dioxide. The carbon dioxide causes the polyurethane to expand into a foamed cellular structure, i.e., a polyurethane foam, which serves to protect the packaged product.
In other types of foam-in-place packaging, the foam precursors are injected into a plastic bag, which is then dropped into a container holding the product to be cushioned. The rising foam again tends to expand into the available space, but does so inside the bag. Because the bags are formed of flexible plastic, they form individual custom foam cushions for the packaged products. In several techniques, a specific apparatus is used to make the bag from plastic film while concurrently injecting it with foam. Exemplary systems for making such ‘foam-in-bag’ packaging cushions are assigned to the assignee hereof, and are illustrated, for example, in U.S. Pat. Nos. 5,027,583, 5,376,219, 6,003,288, 6,675,557, and 7,607,911, the disclosures of each of which are hereby incorporated entirely herein by reference thereto.
While the forgoing systems have been highly successful, the inventors hereof have devised improvements to such systems.
One aspect for improvement pertains to the expansion of the foam within the bags. Generally, the foam precursors are injected into the bag at a fixed location relative to the width of the bag, such that the resultant foam is left to expand outwards from its initial injection point without further manipulation. In many applications, it is desirable for the foam to be more evenly dispersed within the bag. Ideally, such dispersion would be carried in such a way that a more uniform cushion-thickness results, and so that there is a reduced tendency for the expanding foam to escape the confines of the bag, which generally requires the foam-in-bag system to be shut down for cleaning and removal of the foam.
Another aspect for improvement pertains to the supply of plastic film from which the bags are formed. Generally, such film is supplied in the form of a roll, which tends to be rather heavy and cumbersome, generally weighing in excess of 20 pounds, and often more than 30 pounds. As a result, it would be desirable for an improved film-loading mechanism, which facilitates the film-loading procedure for the operator, i.e., by making it easier to load a fresh film roll onto the machine, but without lengthening or complicating the film-path through the machine.
Accordingly, there remains a need in the art for improvements in dispensing and sealing systems for making foam-in-bag cushions, which overcome the foregoing difficulties.